Color adjustment is the most important part of scanning, but I couldn't find any good reference on the net. thus I'll write down my my own way even if it's not following common processes. hope it'll become of your help :)

Basically, color should be adjusted tonecurves, and use saturation a bit. never use brightness, contrast, e.t.c. because it's the blind way ignoring color conditions.

Although I'm using scanner driver to adjust colors, I'll use Smart Curve on the topic because it can show color histogram accurately & visually. it's 8bf plugin for photoshop, and also works on Xnview or Irfanview, e.t.c.

#1 on the following image is a 16bit/channel raw scan without any color matching profile. I don't use color matching profiles because they're all failed.

Ideally, color adjustment should do 2 times both when scanning and after filtering. but it''ll become too complicated and the ways are differ filtering to filtering, thus I use the raw image resized with bspline (slightly blurred) here.


As computer paintings are drawn on white canvas, I adjust white at the brightest color (R,G,B=255,255,255) first. pick the rightest points of R,G,B, then move it separately at where the rightest peaks of histogram reach at the right edge (#2,#3)

If a canvas isn't white, then adjust it to the color as you see.

Sometimes, some channels might reach at 255 before the white will reach 255,255,255. it maybe saturation problem which scanner couldn't handle. in this case, just ignore it and adjust it later.

Secondly, adjust the dark point. unlike the white, paintings aren't always true black. and since screening divided dark colors randomly, histogram have lost the correct blackness. so I just adjusted black loosely (#4)
[edited Oct.2]
Black balance should be adjusted same way to white balance using a image which has true black (bold letters are good). or else, you couldn't get correct gray colors. one difference is not to adjust the peak of histogram at the left side, adjust the hem of histogram at the left side.

Then I should recover the contrast of the dark which is lost while printing process. using master curves, add contrast on the dark overly, then reduce the brightness of the bright to the point the image looks a bit dull & bright because to add saturation make the image more sharp & dark (#5).

Also if the image has strange hue, correct it with tonecurves (#6). I use 2 points per channel to adjust color balance. because if I try to adjust color balance with pointing only one, the effect will appear at the dark stlongly.

After finished tonecurves adjustment, add saturation a bit.


Although I adjusted saturation after tonecurves in the topic to show the process smartly, I have to repeat tonecurves & saturation adjustment several times in the actual editing.

The above process is a standard way of color adjustment, but some scans having the problem difficult to solve with standard ways.

Hue shift of high saturated red/magenta is one of those problem. in this case, I use replace color tool.


Here is the result. however, there might be more sophisticated way.

WOW... The improvement is amazing!!
Congratulations and thanks for the tutorial!
Can't wait to see more details!

Lol.
but pictures are worth thousand words, so we got over 4000 words here.

o/ looking forward to it.

asterixvader said:
Lol.
but pictures are worth thousand words, so we got over 4000 words here.

Expecting a 4000 words tutorial from midzki by tomorrow
lol

LOL. Go for it midzki-kun!!! õ/

We are cheering for you. :P

mm..the link for the smartcurve plugin is dead >_>

What does Smart Curve do that Photoshop's curves dialog doesn't? It looks the same to me.

I adjust white at the brightest color (R,G,B=255,255,255) first. pick the rightest points of R,G,B, then move it separately at where the rightest peaks of histogram reach at the right edge (#2,#3)

Click the whitepoint picker and click on a white spot in the image to do this automatically.

Sometimes, some channels might reach at 255 before the white will reach 255,255,255. it maybe saturation problem which scanner couldn't handle. in this case, just ignore it and adjust it later.

This isn't ideal, because it's clipping some colors.

I think this happens because some inks, at high saturation, are simply brighter than the paper. Clipping them to the paper brightness will alter the color.

Usually, these saturated colors go away after filtering. So, in theory, a better way to handle this is to descreen before curves. The supersaturated colors are no longer there, so you can set the whitepoint to #FFFFFF without clipping colors.

However, you need to do processing in 16-bit for that to work. PS greycstoration can do this pretty fast on GPU with a good graphics card, but will be very slow on CPU. Not all other plugins support 16-bit (all high-quality plugins will). Depending on filtering and your machine, it may not be worth it.

Secondly, adjust the dark point. unlike the white, paintings aren't always true black. and since screening divided dark colors randomly, histogram have lost the correct blackness

This problem also goes away if you filter before adjusting.

syaoran-kun said:
mm..the link for the smartcurve plugin is dead >_>

please someone find alternative link ;_;

petopeto said:
What does Smart Curve do that Photoshop's curves dialog doesn't? It looks the same to me.

what can do is same but combination of navigation, curves, histogram is very conspicuous. I don't know how better curves CS3 have then CS2, but CS2's dialogs/windows are crap. one of the worst color adjustment application in the world imho.

Click the whitepoint picker and click on a white spot in the image to do this automatically.

I readjust manually after using auto.

I think this happens because some inks, at high saturation, are simply brighter than the paper. Clipping them to the paper brightness will alter the color.

I thought it first, but it already altered before clipping white. I tried some other adjustment, but they were all failed. means the limitation of scanner itself not scanning way.

In CS4, create a curves adjustment layer, and you can adjust curves while showing a histogram, and you can navigate normally. (CS2 and CS3 were more limited.)

http://img12.imageshack.us/img12/7835/cs4curves.jpg (colors zany to show UI)

Not sure what's the latest version but here's 2.1

http://wareseeker.com/download/smartcurve-2.1.rar/6170864

Nice Tut midzki.

aoie_emesai said:
Not sure what's the latest version but here's 2.1

http://wareseeker.com/download/smartcurve-2.1.rar/6170864

Nice Tut midzki.

It points to the same source ;_;

http://tomoyo-loves.sakura.ne.jp/crap/smartcurve.8bf

Updated also the main post. Since the original link is borked i'll leave this on the server for a while.

In addinional infomation following the site, "'SmartCurve doesn't work with the 64-bit version Photoshop CS4"
Then if you using CS3 or under which has only crap tonecurves & dialogs, use this instead.

My God... Where should I start from?

Debbie said:
My God... Where should I start from?

It's like drawing. Gotta learn from the bottom up :)

Drawing bottoms from the start eh? You're showing your true colours now Aoie ;)

Radiosity said:
Drawing bottoms from the start eh? You're showing your true colours now Aoie ;)

lol ^^

Now, I drew that cause someone wanted me to draw a full body :)

She'll have clothes later.

The ultimate solution would be to have have a printing firm screen print a scanner target (a paper printed with color blocks spread over the printing color gamut), and we get noise and color correction profiles for scanners.

kiowa said:
The ultimate solution would be to have have a printing firm screen print a scanner target (a paper printed with color blocks spread over the printing color gamut), and we get noise and color correction profiles for scanners.

we already tried, but failed. not only me, also some other scanners. you know, pireze's scans are got worsen after used a scanner target.

midzki said:
we already tried, but failed. not only me, also some other scanners. you know, pireze's scans are got worsen after used a scanner target.

yeah...Anyway different papers have quite different reflective characteristics so it's impossible to cover all cases with one target.
Also different printing conditions make there to be too many cases to cover so the practical way would still be to adjust by comparing scan to the original...

edited on adjusting black point.

Misc:

All scanner has strange hue which need to be adjusted by naked eyes. for example, canon has red hue, epson has blue hue, e.t.c.

Also you need to adjust RBG balance on white/black points again if paper thickness is different.

If paper is thiner, add satulation a bit more. on the other hand, reduce it for smooth covers.